Honeycomb hydrogen storage structure with restrictive neck

ABSTRACT

Heat transfer management/compartmentalization system for a metal hydride hydrogen storage containment unit. The hydrogen storage alloy is preferably divided into compartments having a honeycomb configuration. Heat exchanger tubing is placed through the compartments to promote heat transfer between the hydrogen storage alloy and the exterior environment.

RELATED APPLICATIONS

[0001] The present invention is a continuation-in-part of co-pendingU.S. patent application Ser. No. 10/143,243, which is assigned to thesame assignee as the current application, entitled “A Honeycomb HydrogenStorage Structure”, filed May 9, 2002, the disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a hydrogen storage unit usinghydrideable metal alloys to store hydrogen, and more particularly to ahydrogen storage unit having compartmentalization and a heat transfersystem within such unit.

BACKGROUND

[0003] In the past considerable attention has been given to the use ofhydrogen as a fuel or fuel supplement. While the world's oil reservesare rapidly being depleted, the supply of hydrogen remains virtuallyunlimited. Hydrogen can be produced from coal, natural gas and otherhydrocarbons, or formed by the electrolysis of water. Moreover hydrogencan be produced without the use of fossil fuels, such as by theelectrolysis of water using renewable energy. Furthermore, hydrogen,although presently more expensive than petroleum, is a relatively lowcost fuel. Hydrogen has the highest density of energy per unit weight ofany chemical fuel and is essentially non-polluting since the mainby-product of burning hydrogen is water.

[0004] While hydrogen has wide potential application as a fuel, a majordrawback in its utilization, especially in mobile uses such as thepowering of vehicles, has been the lack of acceptable hydrogen storagemedium. Conventionally, hydrogen has been stored in a pressure vesselunder a high pressure or stored as a cryogenic liquid, being cooled toan extremely low temperature. Storage of hydrogen as a compressed gasinvolves the use of large and bulky vessels.

[0005] Additionally, transfer is very difficult, since the hydrogen isstored in a large-sized vessel; amount of hydrogen stored in a vessel islimited, due to low density of hydrogen. Furthermore, storage as aliquid presents a serious safety problem when used as a fuel for motorvehicles since hydrogen is extremely flammable. Liquid hydrogen alsomust be kept extremely cold, below −253 degrees C., and is highlyvolatile if spilled. Moreover, liquid hydrogen is expensive to produceand the energy necessary for the liquefaction process is a majorfraction of the energy that can be generated by burning the hydrogen.

[0006] Alternatively, certain metals and alloys have been known topermit reversible storage and release of hydrogen. In this regard, theyhave been considered as a superior hydrogen-storage material, due totheir high hydrogen-storage efficiency. Storage of hydrogen as a solidhydride can provide a greater volumetric storage density than storage asa compressed gas or a liquid in pressure tanks. Also, hydrogen storagein a solid hydride presents fewer safety problems than those caused byhydrogen stored in containers as a gas or a liquid. Solid-phase metal oralloy system can store large amounts of hydrogen by absorbing hydrogenwith a high density and by forming a metal hydride under a specifictemperature/pressure or electrochemical conditions, and hydrogen can bereleased by changing these conditions. Metal hydride systems have theadvantage of high-density hydrogen-storage for long periods of time,since they are formed by the insertion of hydrogen atoms to the crystallattice of a metal. A desirable hydrogen storage material must have ahigh gravimetric and volumetric density, a suitable desorptiontemperature/pressure, good kinetics, good reversibility, resistance topoisoning by contaminants including those present in the hydrogen gasand be of a relatively low cost. If the material fails to possess anyone of these characteristics it will not be acceptable for wide scalecommercial utilization.

[0007] Good reversibility is needed to enable the hydrogen storagematerial to be capable of repeated absorption-desorption cycles withoutsignificant loss of its hydrogen storage capabilities. Good kinetics arenecessary to enable hydrogen to be absorbed or desorbed in a relativelyshort period of time. Resistance to contaminants to which the materialmay be subjected during manufacturing and utilization is required toprevent a degradation of acceptable performance.

[0008] Many metal alloys are recognized as having suitability forhydrogen storage in their atomic and crystalline structures as hydridematerials. While this storage method holds promise to be ultimatelyconvenient and safe; improvements in efficiency and safety are alwayswelcome. This invention provides such improvement.

[0009] It is known that heat transfer capability can enhance or inhibitefficient exchange of hydrogen into and out of metal alloys useful inhydride storage systems, because during hydriding an exothermic reactionoccurs and during dehydriding an endothermic reaction occurs. Suchtransfer is important since metal hydrides, in their hydrided state,being somewhat analogous to metal oxides, borides, and nitrides(“ceramics”) may be considered to be generally insulating materials.Therefore, moving heat within such systems or maintaining preferredtemperature profiles across and through volumes of such storagematerials becomes a crucial factor in metal alloy-metal hydride hydrogenstorage systems. As a general matter, release of hydrogen from thecrystal structure of a metal hydride requires input of some level ofenergy, normally heat. Placement of hydrogen within the crystalstructure of a metal, metal alloy, or other storage system generallyreleases energy, normally heat, providing a highly exothermic reactionof hydriding or placing hydrogen atoms within the crystal structure ofthe hydrideable alloy.

[0010] The heat released from hydrogenation of hydrogen storage alloysmust be removed. Heat ineffectively removed can cause the hydridingprocess to slow down or terminate. This becomes a serious problem whichprevents fast charging. During fast charging, the hydrogen storage alloyis quickly hydrogenated and considerable amounts of heat are produced.The present invention provides for effective removal of the heat causedby the hydrogenation of the hydrogen storage alloys to facilitate fastcharging of the hydride material.

[0011] In light of the heat input and heat dissipation needs of suchsystems, particularly in bulk, and in consideration of the insulatingnature of the hydrided material, it is useful to provide means of heattransfer external to the storage material itself. Others have approachedthis in different ways, one by inclusion of a metal-bristled brush orbrush-like structure within the hydrogen storage alloy, depending uponthe metal bristles to serve as pathways for effective heat transfer.Another has developed a heat-conductive reticulated open-celled “foam”into which the hydrided or hydrideable material is placed. The currentinvention provides for effective heat transfer throughout a hydrogenstorage bed via a compartmentalization scheme using thermally conductivematerial.

[0012] Another recognized difficulty with hydride storage materials isthat as the storage alloy is hydrided, it will generally expand and theparticles of storage material will swell and, often crack. When hydrogenis released, generally on application heat, the storage material orhydrided material will shrink and some particles may collapse. The neteffect of the cycle of repeated expansion and contraction of the storagematerial is comminution of the alloy or hydrided alloy particles intosuccessively finer grains. While this process may be generallybeneficial to the enhancement of overall surface area of the alloy orstorage material surface area, it creates the possibility that theextremely fine particles may sift through the bulk material and settletoward the lower regions of their container and pack more tightly thanis desirable. The highly packed localized high density region mayproduce a great amount of strain on the vessel due to the densificationand expansion (upon charging) of the hydrogen storage material. Thedensification and expansion of the hydrogen storage material provide thepossibility of deformation, cracking, or rupture of the container inwhich the hydrideable material is stored. While pressure relief devicesmay be useful in preventing such undesired occurrences as the containerrupture due to the internal gas pressure of the vessel, pressure reliefdevices are unable to prevent deformation of the vessel resulting fromdensification and expansion of the hydrogen storage alloy. Others haveapproached the problem by dividing the container into simplecompartments in a manner that prevents collection of too many fines in aparticular compartment while allowing free flow of hydrogen gasthroughout the container. The current invention provides for uniformpowder packaging in compartments thereby minimizing the collection ofparticulate hydride fines which cause the difficulties noted earlierwhile providing for thermal heat transfer between the hydrogen storagematerial and the exterior environment.

SUMMARY OF THE INVENTION

[0013] The present invention discloses a hydrogen storage apparatusutilizing compartmentalization and heat transfer within the apparatusand providing heat transfer between the apparatus and the exteriorenvironment. The hydrogen storage apparatus provides a rechargeablecontainer to store and release hydrogen. The container may be a pressurecontainment vessel with an aluminum or aluminum alloy composition. Ahydrogen storage alloy, which stores the hydrogen in hydride form iscontained inside the vessel. The interior of the vessel is divided intomultiple compartments by one or more blocks having a honeycombconfiguration. The blocks are formed of a thermally conductive materialallowing heat to be transferred between the hydrogen storage alloy andthe vessel. A series of heat exchanger tubes adapted to cool or heatsaid hydrogen storage alloy are inserted through the blocks.

[0014] The blocks are composed of a plurality of adjacent cells having awall, an open top, and an open bottom. The blocks may be disc shaped,polygonal shaped, or have various other shapes provided that theinterior of the vessel is divided into a plurality of compartments. Thecell walls are shared between the cells in each block. The cells arepositioned parallel to the axial direction of the vessel. The cells mayhave uniform heights and uniform diameters, however, the cells may haveunequal heights and unequal diameters when needed to uniformly contact acurved interior surface of the vessel or conform to design requirements.The cells generally have a diameter up to 25 mm, preferably between 3 mmand 12 mm, most preferably between 3 mm and 7 mm. The cells have acircular or polygonal cross section. The cells are comprised of athermally conductive metal which is able to withstand the operatingtemperatures and pressures inside the vessel, and has negligiblereactivity with the hydrogen and hydrogen storage alloy. The thermallyconductive metal is selected from a group consisting of stainless steel,Al, Mg, Cu and alloys, composites, or mixtures thereof.

[0015] The blocks may also be comprised of a corrugated material. Thecorrugated metal is comprised of a thermally conductive metal able towithstand the operating temperatures and pressures inside said vesselhaving negligible reactivity with said hydrogen storage alloy. Thethermally conductive metal is selected from a group consisting ofstainless steel, Al, Mg, Cu and alloys, composites, or mixtures thereof.

[0016] The heat exchanger tubing extends the entire length of thevessel. The heat exchanger tubing may consist of multiple U-tubesdisposed throughout the honeycomb blocks. The cells are configured toconform to the shape of said tubing once said tubing is inserted throughsaid cells. To aid in heat transfer between the cells and the tubing andto aid insertion of the tubing through the cells, the tubing may becoated with thermally conductive agents. The heat exchanger tubespreferably carries water, ethylene glycol or mixtures thereof. Thetubing is preferably composed of stainless steel or aluminum.

[0017] The vessel is preferably formed around the blocks thereby makingthe vessel seamless, however, a two piece vessel may be used where theblocks are placed into said vessel and said two pieces are weldedtogether forming a seam in the vessel. The vessel may also be wrapped infiber reinforced composite material such as glass or carbon fiber toprovide additional strength to the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 shows a detailed diagram of the first embodiment of thepresent invention.

[0019]FIG. 2 shows a detailed diagram of the second embodiment of thepresent invention.

[0020]FIG. 3 shows a cross sectional view of the honeycomb configurationof the blocks in accordance with the present invention.

[0021]FIGS. 4a-4 e show alternate honeycomb configurations of the blocksin accordance with the present invention.

[0022]FIG. 5 shows a detailed diagram of the third embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] This invention applies compartmentalization of the hydride bedwithin a pressure containment vessel to reduce hydride fines settlementand packing and improve heat transfer to and from the interior of thehydride bed to the exterior environment. Improvement is made bycompartmentalization in a honeycomb configuration to minimize themovement of alloy or hydride fines into accumulations which may causeexcessive strain on the vessel due to densification and expansion of thehydrogen storage material. The compartmentalization may be accomplishedin numerous ways with the goal being to segregate smaller volumes of thehydrogen storage alloy thereby limiting the travel, and subsequentsettling or accumulation, of the fines which can be expected to begenerated within the material through normal use with repetitivecharge/discharge cycling. This must be accomplished while retaining freegas flow of the stored hydrogen. Tolerances of compartmentalization mustbe close enough to minimize flow of particulate fines yet maintain gasflow sufficient to meet requirements of devices in gas-flowcommunication with the hydride bed container such as fuel cells,engines, recharging devices, as well as other users and suppliers ofhydrogen from the absorbed hydrogen bed container.

[0024] This invention includes not only compartmentalization, but alsoemploys highly heat conductive materials within the hydride bed forenhancement and management of the heat transfer within the system. Thelow thermal conductivity of the hydrogen storage alloy makes itnecessary to enhance the heat transfer through the hydrogen storagealloy. In meeting both the need to prevent material densification andthe need for additional heat transfer, the present invention involvescreating compartments within the vessel using materials having goodheat-transfer characteristics. In this manner, heat transfer to assistin efficient discharging of hydrogen from the storage material andstorage bed generally is enhanced and compartmentalization iseffectively accomplished. The compartments are formed from multiplecells arranged in a honeycomb configuration. The cells preferably arecomposed of materials having exceptional thermal conductivity, but insome circumstances low or variable thermal conductivity across thehydride bed will serve beneficially.

[0025] The present invention utilizes heat exchanger tubing placedthrough the compartmentalized hydride bed to add heat needed forendothermic dehydrogenation and remove the excess heat created by theexothermic hydrogenation of the hydrogen storage alloy. The heatexchanger tubing is placed through the compartments while maintainingthermal contact with the walls of the compartments. To achieve theintimate contact with the hydrogen storage compartments, the walls ofthe compartments may be configured to conform to the shape of the tubesonce the tube are inserted through the compartments. Any number of heatexchanger tubes may be used to accomplish the desired result.

[0026] The present invention provides for storage of hydrogen within apressure containment vessel, however a wide variety of vessels orcontainers may be used in accordance with the present invention. Thepressure containment vessel may be cylindrical with a horizontal axis.The vessel may generally be formed of aluminum or stainless steel andalloys thereof. The vessel may be formed around the contents therebymaking the vessel seamless. The vessel may also be composed of twosections where the contents are placed into the vessel and the twosections are welded together forming a seam in the vessel. The vesselmay have one or more openings designed to allow hydrogen to enter andexit the vessel and allow a continuous cooling/heating stream to flowinto and out of the vessel. Preferably, the vessel has an opening atboth ends, one for hydrogen and one for the cooling/heating stream.Other configurations of openings in the vessel may be used provided thevessel allows hydrogen to enter and exit the vessel and a continuousheating/cooling stream to flow through tubing within the vessel. Whereopenings are utilized on both ends of the vessel, a valve is placed onone end to allow the hydrogen to enter or exit the vessel while notallowing any of the hydrogen storage material to exit the vessel withthe hydrogen. A valve designed to allow the cooling/heating stream tocontinuously enter and exit the vessel is placed on the other end. Toprovide the vessel with additional strength for high pressure operation,a fiber reinforced composite material such as glass or carbon fiber maybe wound around the vessel to help prevent vessel rupture at highpressures.

[0027] The first embodiment 1OA of the present invention is shown inFIG. 1. The hydrogen storage alloy is stored inside one or morehoneycomb configured blocks 16 adjacently disposed within the vessel 11.The blocks 16 may have a disc, polygonal, or other configurationprovided that the blocks compartmentalize the entire interior of thevessel. The vessel has a restrictive neck 12 through which hydrogenenters and exits the vessel.

[0028] In the second embodiment 10B, the vessel 11 has a restrictiveneck at each end. This embodiment is shown in detail in FIG. 2. Therestrictive neck 12 is used for hydrogen to enter or exit the vessel andthe restrictive neck on the opposite end 13 is used for a heat exchangerfluid to simultaneously enter and exit the vessel. When the heatexchanger fluid enters the vessel, the fluid flows into a manifold 14which distributes the fluid to a plurality of heat exchanger tubes 18within the vessel. After the fluid flows through the vessel via the heatexchanger tubes 18, the fluid flows into another manifold 15 whichcombines the streams into a single exit stream which flows out of thevessel 11.

[0029]FIG. 3 shows a cross-sectional view of the cells 19 as disposed inaccordance with the present invention. The cells are positioned parallelto the horizontal axis of the vessel 11. The cells 19 are adjacent toone another forming one or more blocks 16 having a honeycombconfiguration where most of the walls of the cells are shared throughouteach block 16. The cells 19 forming each honeycomb block 16 generallyhave a wall and an opening at each end. The cells may have uniformheights and diameters, however, cells having differing heights anddiameters may be used in accordance with the present invention providedthe blocks are adjacently disposed throughout the vessel. Eachindividual cell may have a circular or polygonal horizontal crosssectional shape, as long as all the compartments throughout the blocks16 are adjacent to each other. Other cell configurations may also beused in accordance with the present invention. FIGS. 4a, 4 c, 4 d, and 4e show a few examples of different polygonal cell designs that may beused in accordance with the present invention. The cells 19 may have adiameter up to 25 mm, however, the diameter of the cells is preferably 3mm and 12 mm, most preferably between 3 mm and 7 mm. The cells 19 may becomposed of Al, Mg, Cu, or another thermally conductive material as longas the material has a negligible reaction with the hydrogen storagematerial and hydrogen.

[0030] The hydrogen storage material may also be stored in blockscomprised of a corrugated material rather than cells. An example of acorrugated material is shown in FIG. 4b. The corrugated material may becomposed of Al, Mg, Cu, or another thermally conductive material as longas the material has a negligible reaction with the hydrogen storagematerial and hydrogen. The corrugated material is well known in the artand is used in a variety of heat exchangers.

[0031] One or more honeycomb configured blocks 16 may be placed withinthe vessel 11 to compartmentalize the interior into a honeycombconfiguration. Where more than one honeycomb block 16 is used, thehoneycomb blocks are positioned back to back throughout the entirevessel 11 thereby compartmentalizing the entire interior of the vessel.The honeycomb blocks may be separated by spaces 17 thus creating flowchannels through which hydrogen can better contact the hydrogen storagematerial. Each block 16 is preferably in thermal contact with the insidewall of the vessel 11 to promote thermal conductivity within the vessel.The blocks 16 may have differing widths and diameters to better conformto the interior of the vessel, however, the cells forming each blockpreferably have equal diameters.

[0032] Heat exchanger tubing 18 is inserted through the honeycomb blocks16 to control the temperature throughout the vessel 11. The heatexchanger tubing 18 is inserted through each block 16 via the cells 19throughout the entire length of the vessel 11. In the preferredembodiment, a plurality of U shaped tubes are used. The cells 19 areconfigured to conform to the shape of the heat exchanger tubing 18 oncethe heat exchanger tubing is inserted through the cells 19 therebyassuring thermal contact between the heat exchanger tubing and thecells. Thermally conductive grease or oil may be placed on the outsideof the heat exchanger tubing 18 to aid in insertion of the heatexchanger tubing 18 through the cells 19 and aid in heat transferbetween the cells and the heat exchanger tubing. The amount of heatexchanger tubing 18 within the vessel 11 is variant upon the amount ofheat required to be added or removed from the vessel. The heat exchangertubing 18 transports a cooling/heating liquid through the tubes toremove excess heat to the outside environment during hydrogenation ofthe hydrogen storage material or add heat to the hydrogen storagematerial during dehydrogenation. The cooling/heating liquid ispreferably either ethylene glycol, water, or a mixture thereof, however,other liquids or gases may be used in accordance with the presentinvention. The heat exchanger tubing 18 may be composed of stainlesssteel or aluminum. Other materials may be substituted provided they havenegligible reactivity within the system.

[0033] In a third embodiment 10C shown in FIG. 5, the hydrogen entersthrough a restrictive neck at one end 22 of the vessel 11 and exits atthe opposite end 23 through another restrictive neck. In thisembodiment, the heat exchanger tubes 18 are inserted through the vesselrather than being contained inside the vessel. The heat exchanger tubingis inserted through the cells as in the preferred embodiment. However,due to this design, the entire interior of the vessel is capable ofbeing compartmentalized unlike the second embodiment where interiorspace must be allotted for the manifolds and the U shaped heat exchangertubes. The heat exchanger fluid flows into one end 24 of the vessel andexits at the opposite end 25. This embodiment is designed for use atlower pressures due to the multiple openings in the vessel.

[0034] The vessel is preferably constructed from a container having acylindrical shape, however, vessels having different shapes may be usedin accordance with the present invention. To construct the presentinvention, one or more honeycomb blocks are required. The honeycombblocks are preferably the same size, however, blocks with differingsizes may be used to better compartmentalize the entire interior of thevessel. Smaller honeycomb blocks are used to optimize thecompartmentalization within the vessel. Heat exchanger tubing isinserted through the cells disposed within the honeycomb blocks. Thehoneycomb blocks are thereby positioned back to back with heat exchangertubing extending throughout the series of honeycomb blocks. As the heatexchanger tubing is inserted through the cells, the cells conform to theshape of the tubing assuring thermal contact between the cells and thetubing. The cells and the tubing together form the honeycomb hydrogenstorage structure. Once the honeycomb hydrogen storage structure hasbeen assembled, it is placed into a pressure containment vessel.

[0035] The vessel may be formed having a restrictive neck on one or bothends. The restrictive neck is preferably formed using a spinningprocess. Prior to the spinning process, the honeycomb hydrogen storagestructure is placed inside a cylindrical structure having at least oneopen end. The cylindrical structure is then placed on a spindle with theopen end facing up. A spinning roller is then placed in frictionalcontact with the edge of the open end. The open end is heated and thespindle begins spinning the cylindrical structure. The spinning rollerapplies force to the open end of the cylindrical structure and the openend deforms to form a restrictive neck. Resulting is a seamless pressurecontainment vessel having a restrictive neck. Alternatively, thecylindrical structure may be heated and depressed in a mold to form apressure containment vessel having a restrictive neck. Once therestrictive necks on the honeycomb hydrogen storage structure areformed, the vessel is allowed to cool and a hydrogen storage material ispoured into an opening at one of the ends of the vessel. Due to thepositioning of the cells with respect to each other, the hydrogenstorage material filters through the cells until all of the cells arefilled. Valves are then inserted into the restrictive necks and thevessel is sealed.

[0036] The hydrogen storage alloy may include a variety of metallicmaterials for hydrogen-storage, e.g., Mg, Mg—Ni, Mg—Cu, Ti—Fe, Ti—Ni,Mm—Co, Ti—Mn, La—Ni, Rare Earth-Nickel, and Mm—Ni alloy systems(wherein, Mm is Misch metal, which is a rare-earth metal orcombination/alloy of rare-earth metals).

[0037] Of these materials, the Mg alloy systems can store relativelylarge amounts of hydrogen per unit weight of the storage material.However, heat energy must be supplied to release the hydrogen stored inthe alloy, because of its low hydrogen dissociation equilibrium pressureat room temperature. Moreover, release of hydrogen can be made, only ata high temperature of over 250° C. along with the consumption of largeamounts of energy.

[0038] The rare-earth (Misch metal) alloys have their own problems.Although they typically can efficiently absorb and release hydrogen atroom temperature, based on the fact that it has a hydrogen dissociationequilibrium pressure on the order of several atmospheres at roomtemperature, their hydrogen-storage capacity per unit weight is lowerthan any other hydrogen-storage material and they are very expensive.

[0039] The Ti—Fe alloy system, which has been considered as a typicaland superior material of the titanium alloy systems, has the advantagesthat it is relatively inexpensive and the hydrogen dissociationequilibrium pressure of hydrogen is several atmospheres at roomtemperature. However, since it requires a high temperature of about 350°C. and a high pressure of over 30 atmospheres for initial hydrogenation,the alloy system provides relatively low hydrogen absorption/desorptionrate. Also, it has a hysteresis problem which hinders the completerelease of hydrogen stored therein.

[0040] The Ti—Mn alloy has excellent room temperature kinetics andplateau pressures. The Ti—Mn alloy system has been reported to have ahigh hydrogen-storage efficiency and a proper hydrogen dissociationequilibrium pressure, since it has a high affinity for hydrogen and lowatomic weight to allow large amounts of hydrogen-storage per unitweight.

[0041] A generic formula for the Ti—Mn alloy is:Ti_(Q-X)Zr_(X)Mn_(Z-Y)A_(Y), where A is generally one or more of V, Cr,Fe, Ni and Al. Most preferably A is one or more of V, Cr, and Fe. Thesubscript Q is preferably between 0.9 and 1.1, and most preferably Q is1.0. The subscript X is between 0.0 and 0.35, more preferably X isbetween 0.1 and 0.2, and most preferably X is between 0.1 and 0.15. Thesubscript Y is preferably between 0.3 and 1.8, more preferably Y isbetween 0.6 and 1.2, and most preferably Y is between 0.6 and 1.0. Thesubscript Z is preferably between 1.8 and 2.1, and most preferably Z isbetween 1.8 and 2.0. The alloys are generally single phase materials,exhibiting a hexagonal C₁₄ Laves phase crystalline structure.

[0042] The foregoing is provided for purposes of explaining anddisclosing preferred embodiments of the present invention. Modificationsand adaptations to the described embodiments, particularly involvingchanges to the shape of the vessel, the type of hydrogen storage alloy,the shape and design of the compartments within the storage vessel, andthe shape and design of the heat exchanger tubing will be apparent tothose skilled in the art. These changes and others may be made withoutdeparting from the scope or spirit of the invention in the followingclaims.

1. Apparatus for storing hydrogen storage material under pressure, saidapparatus comprising: a pressure containment vessel defining an interiorvolume having at least one restrictive neck; at least one block having ahoneycomb configuration; and said block operatively disposed in at leasta portion of the interior volume of the vessel and adapted to receivehydrogen storage alloy therein.
 2. The apparatus according to claim 1,wherein a hydrogen storage alloy occupies at least a portion of saidinterior volume of said vessel.
 3. The apparatus according to claim 1,wherein said blocks are in thermal contact with said vessel.
 4. Theapparatus according to claim 1, wherein said blocks have a disc orpolygonal shape.
 5. The apparatus according to claim 1, wherein saidblocks comprise a plurality of adjacent cells having a cell wall, anopen top, and an open bottom.
 6. The apparatus according to claim 5,wherein said cell walls are shared between said cells.
 7. The apparatusaccording to claim 5, wherein said pressure containment vessel has ahorizontal axis.
 8. The apparatus according to claim 7, wherein saidcells are positioned parallel to said horizontal axis.
 9. The apparatusaccording to claim 5, wherein said cells have a diameter up to 25 mm.10. The apparatus according to claim 9, wherein said cells have adiameter between 3 mm and 7 mm.
 11. The apparatus according to claim 5,wherein said cells have a circular cross section.
 12. The apparatusaccording to claim 5, wherein said cells have a polygonal cross section.13. The apparatus according to claim 5, wherein said cells are comprisedof a thermally conductive metal able to withstand the operatingtemperatures and pressures inside said vessel having negligiblereactivity with said hydrogen and said hydrogen storage alloy.
 14. Theapparatus according to claim 13, wherein said thermally conductive metalis selected from a group consisting of stainless steel, Al, Mg, Cu andalloys or mixtures thereof.
 15. The apparatus according to claim 14,wherein said cells are comprised of an aluminum alloy.
 16. The apparatusaccording to claim 5, wherein at least one heat exchanger tube adaptedto thermally treat said interior volume of said vessel is insertedthrough said block.
 17. The apparatus according to claim 16, whereinsaid series of heat exchanger tubes extends the entire length of thevessel.
 18. The apparatus according to claim 17, wherein said cells areconfigured to conform to the shape of said heat exchanger tubes oncesaid heat exchanger tubes are inserted through said cells.
 19. Theapparatus according to claim 16, wherein said heat exchanger tubes arecoated with thermally conductive grease or oil.
 20. The apparatusaccording to claim 16, wherein said heat exchanger tubes carry a heatexchanger liquid.
 21. The apparatus according to claim 20, wherein saidheat exchanger liquid is water, ethylene glycol, or a mixture thereof.22. The apparatus according to claim 20, wherein said heat exchangerliquid enters said vessel and is distributed to said one or more heatexchanger tubes with a manifold.
 23. The apparatus according to claim22, wherein said heat exchanger liquid flowing through said heatexchanger tubes is combined inside said vessel to form a single streamexiting said vessel.
 24. The apparatus according to claim 16, whereinsaid heat exchanger tuber are comprised of aluminum, stainless steel, oranother conductive metal.
 25. The apparatus according to claim 24,wherein said heat exchanger tubes are comprised of stainless steel. 26.The apparatus according to claim 24, wherein said heat exchanger tubesare comprised of aluminum.
 27. The apparatus according to claim 1,wherein said blocks are comprised of a corrugated material.
 28. Theapparatus according to claim 27, wherein said corrugated metal iscomprised of a thermally conductive metal able to withstand theoperating temperatures and pressures inside said vessel havingnegligible reactivity with said hydrogen and said hydrogen storagealloy.
 29. The apparatus according to claim 28, wherein said thermallyconductive metal is selected from a group consisting of stainless steel,Al, Mg, Cu and alloys or mixtures thereof.
 30. The apparatus accordingto claim 29, wherein said thermally conductive metal is an aluminumalloy.
 31. The apparatus according to claim 1, wherein said vessel iscomprised of aluminum, stainless steel, other metals, alloys thereof,polymers, or composites.
 32. The apparatus according to claim 1, whereinsaid vessel is wrapped in a fiber reinforced composite material.
 33. Theapparatus according to claim 32, wherein said fiber reinforced compositematerial is a carbon fiber.
 34. The apparatus according to claim 32,wherein said fiber reinforced composite material is a glass fiber. 35.The apparatus according to claim 33, wherein said restrictive neck isformed using a spinning process.
 36. A process for constructing acompartmentalized hydrogen storage vessel comprising: placing ahoneycomb configured compartmentalization structure inside a metalliccylindrical structure having at least one opening; inserting at leastone heat exchanger tube adapted to thermally treat said interior volumeof said vessel through said honeycomb configured compartmentalizationstructure; forming a restrictive neck from said opening using a spinningprocess; and filling said honeycomb configured compartmentalizationstructure with a hydrogen storage alloy.
 37. The process according toclaim 36, wherein said honeycomb configured compartmentalizationstructure comprises at least one block having a honeycomb-configuration.38. The process according to claim 37, wherein said blocks comprise aplurality of adjacent cells having a cell wall, an open top, and an openbottom.
 39. The process according to claim 38, wherein said cells areconfigured to conform to the shape of said heat exchanger tubes oncesaid heat exchanger tubes are inserted through said cells.
 40. Theprocess according to claim 38, wherein said blocks are comprised of acorrugated material.